The present invention relates in general to optical fiber light transmission systems, and in particular to connectors for use in coupling optical fiber conductors together.
Prior art fiber optic cable connectors have been provided for joining cables which contain optical fibers. The cables are coupled so that the optical fibers of the different cables are aligned for transmitting light signals therebetween. In some applications, the cable connectors are coupled and decoupled numerous times for temporary installations, and may also be exposed to contaminants such as moisture, dust, smoke and fumes. Such fiber optic connectors and cables have been provided for single-channel applications, in which only a single conductor fiber is coupled from each of matting cables, and multi-channel applications, in which each of the cables contains multiple conductor fibers which are coupled by mating connectors. Terminal ends of the optical fibers contained in such cables are included within termini. The termini typically include ferrules which extend over the terminal ends of the fibers and which are aligned to align the mating faces of the respective optical fibers being joined. The terminal end portions of the optical fibers pass through the ferrules, and usually fit flush with terminal ends of the ferrules. When two of the cables are coupled together, opposing ferrules are mated together in an abutting arrangement, with the terminal ends of the optical fibers coaxially aligned for transmitting light signals therebetween. The alignment between two of the mating ferrules is critical in order to eliminate transmission losses which occur due to diffusion and reflection of the light being transmitted from one optical fiber to another.
In some single channel and multi-channel applications, light signals have been transmitted between opposing optical fibers using expanded beam type termini connections, in which the light signal from a first one of the optical fibers is expanded, or spread apart, and then collimated upon exiting a terminal end of a first one of the mating termini, and then is received and collected by a second one of the termini to focus the light signal into a second one of the optical fibers. Expanded beam type termini connectors have encountered losses in excess of 3 db, which is unacceptable in some fiber optic applications. The ferrules of the expanded beam type optical fiber termini have been coupled utilizing split sleeves. The split sleeves are each split along one side by a slot that runs the full longitudinal lengths of respective ones of the sleeves, typically parallel to the lengths of the optical fibers, so that the sleeve acts like a resilient, spring-like member to clamp down upon the exterior of the ferrules to align the two mating ferrules. The two mating termini are usually gimbaled at points which are spaced apart from the terminal ends thereof, such that the terminal ends of the termini are free to angularly move along arcuate paths which extend transversely to the longitudinal length of the sleeve and the light path. This allows the terminal ends of the termini, that is, the axes of the termini, and the optical fibers to be coaxially aligned when being fitted within the split sleeve. O-ring seals have been included to prevent contamination of the terminal ends surfaces of the termini. In some prior art connectors, O-ring seals have been used to seal against the respective ones of the termini, and also to simultaneously provide gimbal surfaces for allowing angular alignment of the axes of the termini, such that the terminal ends of the termini are aligned in parallel.
Connection of male and female fiber optic cables in the field requires that the connecting fiber optic cables be arranged such that respective male and female connector ends of the cables are aligned for mating. The termini in the connectors are usually designated pin or socket, and can be fitted with springs on one or both. The distinguishing feature between a pin and a socket is that an outer alignment sleeve is associated with the socket and remains associated with the socket during normal mate and demate of the connectors, in which a pin termini engages within a socket termini. The male and female connectors typically have a respective pin termini or socket termini, and the connectors are connected to opposite ends of the fiber optic cables. Longer fiber optic cables may be used to prevent the higher transmission losses for connections between the cables by requiring fewer cable connections. If one of the longer cables has been laid out in the wrong orientation for connecting to an adjacent cable, then that one of the cables has to be gathered and then laid out a second time or a special female-to-female or male-to-male connector adapter is required to join two adjacent ends of the cables. Additional handling of connector ends can result in contamination of the termini, and use of special connector adapters results in additional line losses from the added fiber optic connections. To overcome this problem, hermaphroditic fiber optic cable connectors have been used to provide identical cable ends which may be mated together, such that either end of a first cable may be connected to either end of a second cable. Hermaphroditic connectors allow the fiber optic cables to be laid out without regard to the orientation of the cables, and also reduce line losses by not requiring special cable adapters for different cable ends. However, the termini in such connectors still typically remain either pin or socket termini, that is, with an outer alignment sleeve associated with one or the other.
A multi-channel fiber optic cable connector is provided for aligning the terminal ends of optical fibers of fiber optic cables for transmitting light signals therebetween. Termini are provided which include end portions defined by ferrules that extend around terminal ends of the optical fibers. The termini are independently gimbaled, with gimbal points being disposed distally from respective mating planes defined by opposing terminal ends of the termini. Alignment sleeves are provided to align the adjacent termini of optical fibers included within respective ones of the fiber optic cables. The alignment sleeves have internal bores that are slightly larger in size than the outside diameters of the peripheries of the termini defined by ferrules, providing a clearance fit between the ceramic alignment sleeves and respective ones of the termini. The tubular bodies of the alignment sleeves are preferably formed of ceramic and have continuous cross-sections in various sectioning planes.